chatgpt wrote the database layer for me

src/types.hpp

@@ -1 +1,97 @@
 #pragma once
+
+#include <memory>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include <clickhouse/client.h>
+#include "skwyward-api-utils.hpp"
+
+namespace database_utils {
+
+// ---------- DB Handle ----------
+
+using CHClient = std::shared_ptr<clickhouse::Client>;
+
+// ---------- User ----------
+
+struct UserRecord {
+    std::string user_id;     // UUID
+    api_utils::Login login;
+};
+
+// ---------- Snapshot ----------
+
+struct GradeSnapshot {
+    std::string response_id;
+    api_utils::GradesResponse response;
+};
+
+// ---------- Assignment Diff ----------
+
+struct AssignmentDiff {
+    std::string class_grade_id;
+    std::string assignment_id;
+
+    std::optional<api_utils::AssignmentGrade> old_grade;
+    api_utils::AssignmentGrade new_grade;
+};
+
+// ---------- User ops ----------
+
+std::vector<UserRecord>
+get_all_users(const CHClient& client);
+
+bool
+register_user(
+    const CHClient& client,
+    const std::string& username,
+    const std::string& password
+);
+
+bool
+authenticate_user(
+    const CHClient& client,
+    const std::string& username,
+    const std::string& password
+);
+
+// ---------- Grades ----------
+
+std::optional<GradeSnapshot>
+load_latest_grades(
+    const CHClient& client,
+    const std::string& user_id
+);
+
+// ---------- Diff ----------
+
+std::vector<AssignmentDiff>
+diff_grade_responses(
+    const api_utils::GradesResponse& old_resp,
+    const api_utils::GradesResponse& new_resp
+);
+
+// ---------- Conditional insert ----------
+
+bool
+conditionally_insert_grades(
+    const CHClient& client,
+    const std::string& user_id,
+    const api_utils::GradesResponse& new_resp
+);
+
+// ---------- Persist diffs ----------
+
+void
+insert_grade_updates(
+    const CHClient& client,
+    const std::string& user_id,
+    const std::string& old_response_id,
+    const std::string& new_response_id,
+    const std::vector<AssignmentDiff>& diffs
+);
+
+} // namespace database_utils
+